cold-start 20v 4age blacktop runs terribly… please help

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This is part 7of a multi part video series about how to troubleshoot any ignition, fuel injection or timing issue. I describe the sensors and how to troubleshoot them: Throttle Position Sensor (TPS), 2) Manifold Absolute Pressure (MAP), Intake Air Temperature (IAT), Engine Coolant Temperature (ECT), Engine Temperature sensor for the gauge in your dash, Knock Sensor (KS) TPS – dtc 21 or 22, variable resistor. checking wire harness grey(+) to black should show 5Vdc from ECM. From sensor, signal (dk blue wire) to common (blk wire) should show ~7Kohms at WOT and 1.9kohms @ throttle closed. Should be smooth resistance changes while adjusting TPS position. MAP – just disconnect it. if problem goes away replace the MAP IAT- 8kohms @-5 deg C, 2.2kohms @ 37 deg C, 5 VDC from ECM ECT – 177 ohms @ 100 degC, 2238ohms @ 30 degC, 3520 @ 20 deg C, 9420 ohms @ 0 degC, 21.4k ohms @ -15 deg C. When these fail, they fail with higher resistance, telling the ECM it is too cold which causes the ECM to richen the mixture. Note: there is a separate video for the EGR valve (part 6 in the series)


46 Responses to “cold-start 20v 4age blacktop runs terribly… please help”

  1. kimgulle says:

    Well it runs lean, that’s for sure. But i guess you’ve already solved it? The first step i would take is change the coolant temp sensor though.

  2. fisqual says:

    @asiancustoms LOL!!
    

  3. asiancustoms says:

    sounds fuckin awesome you should keep it the way it is or nos kit

  4. bergerbrother says:

    wtf a fire comes out from your TB..i never saw it before.

  5. fisqual says:

    @TheLancergsr wasn’t map sensor. read other comments

  6. TheLancergsr says:

    get a new map sensor

  7. fisqual says:

    @eishiba I know I’m a little slow (6 months slow, lol). It’s an ’84 Corolla SR-5 hatch.

  8. eishiba says:

    what kind of car is this?

  9. fisqual says:

    No, it didn’t do that if I d/c the map. It was just a few loose wires.

  10. fisqual says:

    No, all stock. AND, it’s pretty much fixed. I’m getting 36/29MPG, Hesitation is gone. It’s running a little rich, but I think these tend to. I just need to tune it now, and it will be perfect.

  11. 4B1D3N1 says:

    Are those aftermarket ITBs?
    If so you need a new ECU or you need to remap yours..

  12. MonkiMajyk says:

    you solved it right?

  13. fisqual says:

    It’s possible that my MAP sensor isn’t correct? I bought it on ebay as being for the 4age – but I also pulled a few off of some 4AFEs and 5SFE and 3SFE and tried those too, but they all seemed the same (as mixture and idle goes).

    My TPS is within factory spec.
    VVT comes on when I have my gas pedal more than about 65% down or between 4000 and 6000rpm.

    My car doesn’t backfire anymore though, just high idle and running rich.

  14. fisqual says:

    No the ISCV is fine. The ISCV shuts when I ground RSC and opens when I ground RSO (500 and 4000 rpm). My Oxygen sensor is still throwing a code even tho the people on club4ag swear that my O2 sensor is ‘compatible’.

    I don’t think an O2 sensor would cause high idle though. my Scion o2 went out a few months ago and it ran/idled fine, just used a little more gas.

  15. ToyCrazyNZ says:

    good idea hi idle cud be caused by few things. iscv (idle valve) wud be my guess tho. blacktops are known for clogging up the inlet from blow by. if u pull the hoses off iscv n spray some carb cleaner down thru it, see if that helps. is the TPS set correctly? is the map sensor getting vacuum from the correct port? backfiring out throttles (pl) wud usually be over advanced ignition timing or advanced inlet cam. but could be to do with vvt coming on early due 2 wrong or faulty map sensor signal?

  16. fisqual says:

    H2o temp sensor wasn’t grounded enough. I grounded it to the body and now it’s running better. (not perfectly though)

  17. fisqual says:

    There’s a vac rail on the back of the ITBs behind the throttle plates and it should measure properly even without the air box installed.

  18. fisqual says:

    It’s the stock blacktop. Map sensor is fine. I measured the vacuum on it and the ohms and such vs the factory service manual.

  19. fisqual says:

    I can’t really set my base timing b/c it won’t idle properly (it sits at 1800-2000). I’ve messed with it + and – though, and do have a timing gun, and do know how to go into diag and stuff.

    That problem is fixed, I should post new vids about my problems now.

  20. fisqual says:

    STA wire is hooked up. Thanks for the suggestion.

    That particular problem is fixed now though.

  21. SOTOSDR says:

    The only think to do is to conect the STA wire in the ECU.The STA is a signal +12 volt from the starter of the engine to the STA pin of the ECU. +12 volt when you start your engine and 0 volt when the engine work. The STA wire is very important for this ECU.If you need more info just ask me.

  22. ImPeakingBrah09 says:

    get a rotor..

  23. 4age20vbt says:

    I was having a similar problem with mine especially during cold wether startups. The problem…..Ignition timing was too ADVANCED!! I guess I was a tooth off on the CRANKSHAFT from when I replaced the timing belt. Remove the top timing cover and check your cams for proper alignment and make sure the crank is at 0 degrees also. Next also do what ToyCrazyNZ reccomends about checking for base timing. Good luck. Let me know if this helps.

  24. ToyCrazyNZ says:

    what ecu are you running? stock blacktop should run fine. have you checked the cam pulleys are in correct position? and have you timed the ignition to 10degrees BTDC with the diagnostic connector T and E1 bridged? the map sensor gets its air from the inlet manifold on the head flange so it doesn’t matter if you have an airbox.. but is your map sensor connected to the right place?

  25. j00hz says:

    removing the MAP sensor wont do much.. you need to get an aftermarket ecu and get it tuned to eliminate the sensor . therefor you can add ITBs

    when you connect that sensor is sensing no air flowing past. only way is to

    1. new ecu or remap for ITB
    2. put the plenum back on it and have it runing through the stock piping and airbox with map in.

  26. MrMusicDreamz says:

    PCV, Positive Crankcase Ventilation, you deserve to know! BTW, I have to commend you on this series! There are other sensors I have not seen, The MAF And the Crank Position Sensor. The CPS will keep you from starting but the maf is notoriously known for running rich in GMs. I sure wished someone could tell me where that is on my Lumina car or my Astro for that matter! On my Astro, the cps is under my rotar, pretty easy with that. Don’t forget the guy who prototyped much of this o2, in exhaust.

  27. mrsillyman says:

    @jeffries31 the truck was not running when this video was taken. What you are hearing is a ticking noise that my $99 after tax digital camera injects whenever it records a video… it has done that since new… not sure why.

  28. jeffries31 says:

    your truck has a ping sound in the background is that normal ?

  29. mrsillyman says:

    @jhep1985 I am not an expert on knock sensors but there are usually 2, one on each side of the engine (1 for each bank of cylinders). I have also read that they are very prone to failure if the engine is pressure washed…

  30. jhep1985 says:

    hi .. i have a question i have a 2001 gmc yukon 2wd 4.8 i went to place to check my car and the computer show knock sensor defective ,,i want to know how many knock sensor my truck has ?

  31. mrsillyman says:

    @kc88kc hi there… no spark or fuel pressure… hmmm…not a fuel pump issue… i am thinking the easiest thing is troubleshoot why the fuel pump is not working… that would be way easier than trouble shooting the ignition… check all your fuses for starters… then try to manually engage your fuel pump (should be a test plug under the hood to trigger the pump). get a manual and go from there on fuel pump tests.

  32. kc88kc says:

    hey bro i need some help i have a 1996 chevy s10 2.2 l and it wont start the weird thing is it gets no spark and no fuel pressure i have replaced the fuel pump and the cables for the plugs still no spark or fuel pressure im thinking it is the computer or some type of senser could you help me with this personal message if you could be a big help right now..
    .ps. it was working fine until i ran out of gas and put more gas in it and haveing these problems please help me thanks

  33. spelunkerd says:

    As we become more and more dependent on OBD codes to make a diagnosis, it makes it even more important to emphasize those situations where codes don’t show up. I’ve often wondered whether poor fuel efficiency is due to ‘silent’ sensor malfunction. This is a really good review, thanks for posting.

  34. mrsillyman says:

    hi there – on my 94 4.3 it had 2 sensors. the one on the drivers side between the back 2 spark plugs was for the dash gauge. the one that was nearly impossible to see without a flashlight was behind my coolant thermostat. it took 3 tries for me to find it but… it was there. i would call GM if I were you. with your VIN they can tell you the # of sensors and probably location.

  35. 121sabritas says:

    ok,i have 2001 chevy s10 v6 has 2 temperature sensors? I look at my motor and I’m looking at 1 and actually ask the auto parts store and only shows 1 you now ? some help please

  36. mrsillyman says:

    hi there… i am having trouble understanding your description about horns and boards… the temp sensor is typically all the way cold upon startup with a cold engine and about 40-50% when fully warm. if you have temp readings higher or lower than that range when warm you might have a stuck open (runs cool) or stuck closed (runs hot) thermostat. Most engines have separate temp sensors for the dash gauge and for the computer…and they have no impact on each other.

  37. 121sabritas says:

    Hi I have a question? I have a 2001 chevy s10 v6 temperature till my board marks almost 1 / 2 and the manual horn design that is almost 1 / 4 or is it normal that you recommend? change the 2 temperature sensors

  38. muchtooffer48 says:

    Thank you so much. This car may be running richer than yours. I’ve never seen anything like it. Years ago my company had a ”old school” fork lift that ran that way. I replaced everything, but I never did get it to lean out. I’ll get up with you later. Frank.

  39. mrsillyman says:

    Hi there,
    thanks for the comments. you likely won’t get any codes unless you can actually run it at highway speeds.  Until then, i would check engine temp sensor (NOT the guage temp sensor), O2 sensor, dirty stuck injector, fuel pressure and regulator, grounds to the computer. I think I have some other videos that cover all these checks if they aren’t covered in part 7. good luck and let us know how you make out.

  40. muchtooffer48 says:

    I have a 1993 chevy 3.1 that is running supper rich. Just like your truck. And it is a convert., so I’m wanting to drive it now. I’m thinking it is the engine temp. sensor. By the way, thank you for this info. I have no codes which is strange. What do you think about that? Thank you. Frank.

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